A new study suggests that Mars had an oxygen-rich environment long ago -- even before Earth.

Oxford University researchers, led by Professor Bernard Wood of Oxford University's Department of Earth Sciences, compared meteorites and surface rocks before coming to this conclusion.

The team studied meteorites from Mars and rocks found by NASA's Spirit rover on Mars' surface. They found that the surface rocks were five times richer in nickel than the meteorites.

They believe this is the case because of subduction, where material is recycled into the planet's interior. The study says that Mars' surface was oxidized long ago, and through subduction, materials rich in oxygen went into the planet's interior and were recycled back to the surface about 4000 million years ago. Earth didn't experience a rise in atmospheric oxygen until 2500 million years ago.

The meteorites, though, are younger rocks that came from deep within the red planet. Hence, they are unphased by this subduction.

"What we have shown is that both meteorites and surface volcanic rocks are consistent with similar origins in the deep interior of Mars but that the surface rocks come from a more oxygen-rich environment, probably caused by recycling of oxygen-rich materials into the interior," said Wood. "This result is surprising because while the meteorites are geologically 'young', around 180 million to 1400 million years old, the Spirit rover was analysing a very old part of Mars, more than 3700 million years old."

Spirit, a golf cart-sized, solar-powered robot geologist that was sent to Mars in 2004, spent six long years traveling the Martian surface. But after enduring many harsh winters on Mars, Spirit finally fell silent in 2010, and was removed from the mission in mid-2011.

NASA has been relying on rover Curiosity to dig up new info on the red planet now. It landed on Mars in August 2012, and has found rock samples that suggest life on Mars and questionable radiation levels that could determine human travel to Mars.

quote: One would hope that if enough mass is added to Deimos, the core of Mars would unlock due to tidal stress induced heat. Maybe Mars could be habitable with a magnetosphere.

First, you'd need to make it seriously more massive to have any meaningful effect. Even Deimos and Phobos combined aren't enough to do anything.

Second, It's mostly a matter of primordial heat, and radiodecay of unstable elements in its mass, not 'tidal stress.' A larger sphere is going to lose less heat through its surface area, average density and all other things being equal, than a smaller one. Mars simply cooled off faster, Earth's moon faster still. Eventually Earth will become geologically dead, too. But not anytime soon. (IIRC. the Magellan orbiter may have detected current volcanic activity on the slightly less massive, slow rotating, moonless Venus.)